1. Field of the Invention
The present invention relates to an imaging apparatus and a control method therefor. More particularly, the present invention relates to an imaging apparatus having an autofocus (AF) function, and a control method therefor.
2. Description of the Related Art
Generally, an imaging apparatus, such as a digital camera or a video camera, uses an AF system which automatically performs a focusing operation using a luminance signal obtained from an image sensor, such as a charge-coupled device (CCD), as a system to focus on an object by moving the position of a photographic lens. The imaging apparatus using the AF system obtains an in-focus position by detecting a position of the photographic lens at which the highest contrast is obtained, based on a focus signal obtained by integrating high-frequency components of image data in a focusing area set in an image plane.
In order to continue to focus on a moving object, the imaging apparatus using the above AF system needs to continuously drive the photographic lens to obtain an in-focus position. In a case where an in-focus position is continuously obtained, it is useful to store the obtained in-focus position, because the next in-focus position can be predicted from a past in-focus position.
Japanese Patent Application Laid-Open No. 6-201983 discusses an example of such a technique, i.e., an imaging apparatus that causes the AF system to track an object by repeating an operation of moving, before shooting an object, a photographic lens to a position at which high contrast is obtained.
Japanese Patent Application Laid-Open No. 2002-169082 discusses a technique of repeating an operation of storing, at each shooting of an object in a continuous shooting mode or the like, an in-focus position after preliminarily moving a photographic lens to a position at which high contrast is obtained, before shooting, so as to predict an in-focus position at the next shooting and to determine a drive range of the photographic lens.
However, the techniques discussed in Japanese Patent Application Laid-Open Nos. 6-201983 and 2002-169082 have a problem that an operator cannot determine whether an in-focus position in a current focusing state is an initial in-focus position of the photographic lens after issuance of a focusing instruction, and whether the in-focus position in the current focusing state is that of the photographic lens that is obtained after continuous focusing.